1. Field of the Invention
This invention relates to the design of electric circuits, and in particular a machine for assisting a designer in the design and development of electric circuits.
2. Description of Related Art
There are currently available custom designed LSI integrated circuits known as ASICs (application specific integrated circuits) or uncommitted logic arrays (ULA--registered trade mark). These are intended for the customers that may require not only digital functions on a chip, but also input/output, and where appropriate, analogue requirements. In order to make optimum use of such ASICs it is necessary to use an effective computer aided design software system (CAD) which is used for system and interconnection design and also verification of the circuits.
Whilst such CAD systems work satisfactorily with digital circuits which can be tested in software form, the use of such systems for designing analogue circuits and mixtures of analogue and digital circuits has proved far more difficult since it is necessary in order adequately to test an analogue circuit to test its operation in the real world. A common method for simplifying the design of analogue circuits is to build a breadboard in which discrete components and standard integrated circuits are hand wired and then coupling the bread board to the real system. This allows digital voltage meters and oscilloscopes to be connected to points of interest and the external switches sensors and displays to be attached.
Thus although the use of ASIC has decreased the need for breadboarding, CAD systems have only previously proved effective where the bulk of the system is digital. When a significant proportion of the system is linear (i.e. analogue), there is no automatic design system currently available which can adequately cope with the entire design problem.
Papers which illustrate the state of the art are as follows:
1. "Silicon Compilers in an Automated Design Environment" Presented at the 7th International Conference on Custom and Semi Custom ICs Nov. 3/5, 1987, Penta Hotel, Heathrow, G. W. Birchby and D. J. Wardle. PA0 2. "Recent Advances in Gate Array Technology" IEE Colloquium "The impact of ASICs on equipment design" Savoy Place, London Jan. 11, 1988, G. W. Birchby. PA0 3. "Mixed Analogue and Digital Design--the CDI Alternative" Electronic Design Automation Conference, Wembley Conference Centre, June 27/30, 1988, G. W. Birchby.